98 lines
978 B
ArmAsm
98 lines
978 B
ArmAsm
; wires -- Apple II Hires
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; D0+ used by HGR routines
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HGR_COLOR = $E4
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HGR_PAGE = $E6
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GBASL = $26
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GBASH = $27
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COUNT = $FE
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FRAME = $FF
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; soft-switches
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; ROM routines
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HGR2 = $F3D8 ; set hires page2 and clear $4000-$5fff
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WAIT = $FCA8 ; delay 1/2(26+27A+5A^2) us
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wires:
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jsr HGR2
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reset_x:
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ldx #$0
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outer_loop:
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; pulse loop horizontal
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lda #$00
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tay
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sta GBASL
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lda #$40
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sta GBASH
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horiz_loop:
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lda even_lookup,X
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sta (GBASL),Y
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iny
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lda odd_lookup,X
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sta (GBASL),Y
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iny
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bne noflo2
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inc GBASH
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noflo2:
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lda #$44
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cmp GBASH
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bne horiz_loop
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; A should already be $44 here
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; Y should be 0
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vert_loop:
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txa
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clc
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adc #2
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asl
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asl
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adc #$40
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sbc GBASH
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cmp #8
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lda #$81
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bcs noeor
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ora #$02
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noeor:
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sta (GBASL),Y
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inc GBASL
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inc GBASL
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bne noflo
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inc GBASH
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noflo:
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lda #$60
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cmp GBASH
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bne vert_loop
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inx ; wrap at 7
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cpx #7
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beq reset_x
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bne outer_loop
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even_lookup:
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.byte $D7,$DD,$F5, $D5,$D5,$D5,$D5
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odd_lookup:
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.byte $AA,$AA,$AA, $AB,$AE,$BA,$EA
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